Q: I'm trying to build xmlto, but it doesn't work.

A: If you get `Attempt to load network entity' errors when building
   xmlto, your system does not have the required support for XML
   Catalogs
   (http://www.oasis-open.org/committees/entity/spec-2001-08-06.html).
	 Try to reinstall your docbook(xhtml1) dtds or fix your catalogs
   manually. Verbose mode might help to analyze a problem.